Rib Spreading Tool Gets Robotic Update

It may sound unbelievable, but some tools that physicians use to perform invasive surgery were originally developed in the 1930s and have gone through minimal updating since. Most often, these tools have been efficient enough to do the job, even if patients took a long time to heal. This is especially true when a surgeon has to enter the chest cavity for heart or lung operations. To date, there are two primary methods used to open a space large enough for a doctor to work inside the chest: a thoracotomy or a sternotomy.

The thoracotomy is where an incision is made between two ribs to gain access. For a sternotomy, the surgeon saws through the sternum and then spreads it apart. In both cases, the surgeon pries apart the ribs or sternum using a hand-cranked, stepping mechanical jack called a thoracic retractor. Large forces are needed to spread the ribs. In fact, the Physcient team discovered that the forces necessary to separate the ribs are roughly equal to the weight of the person being operated on, which means that using a thoracic retractor can result in broken bones, crushed nerves, wrenched joints, and torn ligaments. All of these factors offer adverse post-surgical effects that can be ongoing.

Detail of a motor housing assembly of a Physcient prototype using the latest motor technology. The Assuage Smart Retractor will require little training and provide a useful tool for surgeons to help patients hurt less and heal faster.

Physcient has developed technologies that are expected to greatly reduce the damage of thoracic retraction. "Two of the concerns we ran into," said Chuck Pell, cofounder (with Hugh Crenshaw) of Physcient, "were that we had to maintain the same footprint as other thoracic retractors being used in the operating room today, plus we had to be able to sterilize the tool repeatedly, to be used for literally hundreds of cycles." The company's Assuage Smart Retractor was designed to apply technology to solve a longstanding problem without changing surgeons' procedures.

According to Pell: "We both (he and Crenshaw) studied biomechanics, and it is that understanding of how creatures move that we use to translate into technology. We recently turned that knowledge to surgical tools, and are finding it very interesting. Many of the tools used in surgery today were invented prior to biomechanics becoming a mature science."

It may be that the software can spread the ribs more gently, or something like that. My feeling is that there are a few details not mentioned in the writeup, although it is at least possible that simply having a different form factor was the large benefit. On some rare occasions the shape of a tool is more important than the actual function of that tool. Not very often, but occasionally.

The real difference is that the software is controlling how much force is placed on the ribs rather than the surgeon. So, do you believe that the machine has a better feel for what's happening to the patient or the surgeon? One could argue that the machine is more objective or that the surgeon knows his patient and procedure better. The medical devices I was involved with were designed to perform a particular way, but the surgeon was always allowed to override the "standard settings", our belief being that the surgeon, much like a pilot, is always in command.

Since ribs are still being spread, probably about the same distance, my guess is that a similar amount of force is being applied.

So while the new system tool is possibly much easier to control, and certainly much more modern in fuctionality, the actual benefit has not been made clear to me. The ribs are still being spread by force, and that force is still about the same, and now a device that does not have intrinsic force feedback is provided. A hand driven jack mechanism provides instant feedback through the feel to the operator, while this system evidently provides a display of the force. Different for sure, but I don't know how much better, since the mechanism of advantages was not explained, I don't think.

We've seen huge advances in medical technology over the past decade. This is another example. Medical technology has become a very exciting are of development. This new technology for helping with chest surgery is good to see.

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